The purpose of this study was to develop new methodologies to measure muscle metabolism and blood flow in older humans, both with normal and reduced blood flow (peripheral vascular disease). Progress in this year was mainly on development of blood flow measures using duplex Doppler. These measurements were compared to NIRS measurements of calf muscle oxygen saturation (n=6, mean age 67 yrs). NIRS (Runman, NIM, Inc) measured the relative oxygen saturation of hemoglobin as the difference in absorption of 750 and 850 nm light. We found that there was a good agreement with the time course of post-ischemic blood flow and the rate of oxygen resaturation. Further studies are planned to confirm this relationship. We also plan to compare duplex Doppler flow measurements with separate PCr recovery measured with magnetic resonance spectroscopy (MRS) in a 2.0 Tesla 78 cm magnet with a 9 cm surface coil placed over the gastrocnemius/soleus muscles. Recovery will be measured after 4 minutes of resting ischemia and after exercise consisted of repeated plantar flexions in a supine position. These studies may lead to improved evaluation of muscle blood flow in elderly subjects.